I have a similar problem with brand new FNS Plus Vert. DE Pentair filter, 48 sqft. IG Vinyl pool, 12K, 1 hp motor (1 speed), NoCal.

The difference being that we're still working on start up due to cartridge filter failing 2 weeks ago. So, algae problem. The difference is that
on the second grid cleaning we discovered that only a top 1/3 band of the filter grids got coated. How would that work with water exposed
areas getting coated only? I read "Use & Care". Of course we always wait for water gush before shutting of air valve.

Also, there's a decent amount of DE powder on the pool floor even though we used a kitchen scale to measure out exactly the recommended 5 lbs.

I'm asking here because if I call service ( our dealer and installer) I won't see them till later next week and there go another bunch of expensive chems..
not to mention that the water is warm & inviting....
thanks

dada

Welcome to TFP!

If DE is getting into the pool, there is something wrong with the filter. The most likely cause is a torn filter grid, though it could also be an improperly assembled filter or a problem with the multi-port valve.

Hi,

Our new filter came with an already obsolete (black) manifold. The problem was a crack real close to the external white pipe air bleed entry.
Since we've had this less than a week and it is a well documented problem, our service company replaced the manifold with the newer model (white).
It is a **** to put together the grids but it was not an operator error... phew!

I'm glad you got that figured out